Tiny Gene Changes Linked to Intelligence

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When it comes to smarts, which is more important — nature or
nurture, genetics or environment? Well, yes, it seems. New
findings now suggest that half of all differences in intelligence
between people appear rooted in the collective influence of many
tiny genetic variations. That leaves plenty of influence open to
other factors, the researchers said.

Past research had suggested that bright parents tend to have
bright
kids. However, the extent to which genetics contributes to
intelligence, as opposed to other contributing factors such as
environment, has been hotly debated.

No single gene variant has yet been identified as reliably linked
with intelligence. Instead, scientists investigated the potential
role of many common genetic variations on
human intelligence.

A gene is a string of molecules known as nucleotides, much as a
word is a sequence of letters. The recipe of nucleotides making
up each gene is not always precise — for instance, the copy of a
gene a person has might differ by one nucleotide from the copy of
that same gene seen in someone else, much as the word "cat"
differs from "car" by a single letter.

Researchers compared nearly 550,000 of these variations, known as
single nucleotide polymorphisms (SNPs, or "snips") with the
performance of more than 3,500 unrelated adults on a pair of
tests of general intelligence — one on problem-solving
skills, the other on acquired knowledge, such as vocabulary.
Genetic variations could explain about half of all the
differences seen in intelligence between people — that is, some
combinations of these variants seem show up more in smart people.

"We have found gene signals associated with cognitive abilities,"
researcher Ian Deary, a psychologist at the University of
Edinburgh in Scotland, told LiveScience.

Although the researchers found that genetic variations can affect
intelligence, they cautioned they do not yet know which genes are
important, or how much each contributes. "The likelihood is that
there are very many genes contributing, each with a small
effect," Deary predicted.

"We are not saying that intelligence is 'fixed' or 'determined'
in our genes," researcher Peter Visscher, a quantitative
geneticist at the Queensland Institute of Medical Research in
Australia, told LiveScience. "We are saying that about 50 percent
of individual differences between people in intelligence is due
to genetics. We are not saying that the environment is
unimportant."

Future research could not only investigate what specific genes
seem linked with intelligence, but how they might interact with
the environment, as well as how these genes impact changes in
cognitive skills with age Deary added. "We want to use these data
to find out why some people's thinking skills age better than
others," Deary said.

The scientists detailed their findings online Aug. 9 in the
journal Molecular Psychiatry.